Method and system for efficient full resolution correlation

ABSTRACT

Aspects of a method and system for efficient full resolution correlation may include correlating a first signal with a second signal at a rate corresponding to a first discrete signal, wherein each sample of the first signal may be generated by summing a plurality of consecutive samples from the first discrete signal, and the second signal may be generated by summing the plurality of consecutive samples from a second discrete signal. The correlating may be performed by a matched filter and/or a correlator. The first signal comprising N samples may be generated by summing L consecutive samples for each of the N samples from the first discrete signal comprising N*L samples. The second signal comprising N samples may be generated by summing L consecutive samples for each of the N samples from the second discrete signal comprising N*L samples. The first signal and the second signal may be correlated by multiplying the N samples of the first signal with the N samples of the second signal in N multipliers and summing a plurality of outputs of the multipliers. A maximum of the correlating may be determined to achieve synchronization between the first discrete signal and the second discrete signal

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

Not applicable

FIELD OF THE INVENTION

Certain embodiments of the invention relate to signal processing. Morespecifically, certain embodiments of the invention relate to a methodand system for efficient full resolution correlation.

BACKGROUND OF THE INVENTION

Electronic communication has become prolific over the last decade. Whileelectronic communication was initially limited to the desktop, recenttrends have been to make communications, media content and the Internetavailable anytime, anywhere and, increasingly, on any device. Alreadynow, it is quite common to find mobile devices such as cellular phonesor Personal Digital Assistants (PDAs) that incorporate a large range ofcommunication technologies and associated software. For example,fully-featured web-browsers, email clients, MP3 players, instantmessenger software, and Voice-over-IP may all be found on some recentdevices.

To support many different communication standards and data formats, itis desirable to use efficient signal processing, which may prolongbattery life in portable devices, and reduce computational complexity.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

A method and/or system for efficient full resolution correlation,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an exemplary multi-radio systemin accordance with an embodiment of the invention.

FIG. 2 is a block diagram of an efficient full resolution correlator, inaccordance with an embodiment of the invention.

FIG. 3 is a flow chart illustrating an exemplary correlation process inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and systemfor efficient full resolution correlation. Aspects of the invention maycomprise correlating a first signal with a second signal at a ratecorresponding to a first discrete signal, wherein each sample of thefirst signal may be generated by summing a plurality of consecutivesamples from the first discrete signal, and the second signal may begenerated by summing the plurality of consecutive samples from a seconddiscrete signal. The correlating may be performed by a matched filterand/or a correlator. The first signal comprising N samples may begenerated by summing L consecutive samples for each of the N samplesfrom the first discrete signal comprising N*L samples. The second signalcomprising N samples may be generated by summing L consecutive samplesfor each of the N samples from the second discrete signal comprising N*Lsamples. The first signal and the second signal may be correlated bymultiplying the N samples of the first signal with the N samples of thesecond signal in N multipliers and summing a plurality of outputs of themultipliers. A maximum of the correlating may be determined to achievesynchronization between the first discrete signal and the seconddiscrete signal.

FIG. 1 is a block diagram illustrating an exemplary multi-radio systemin accordance with an embodiment of the invention. Referring to FIG. 1,there is shown a multi-radio device 102, comprising a processor 104,memory 112, and a plurality of radio transceivers, of which radiotransceiver 106 a, radio transceiver 106 b, and radio receiver 106 c maybe illustrated. The multi-radio device 102 may be communicativelycoupled to one or more antennas, of which antennas 108 a and 108 b maybe illustrated. There is also shown a cellular base station 110 a, aWiMAX base station 110 b, headphones 110 c, a Wireless Local AreaNetwork (WLAN) access point 110 d, and an Ultra-Wideband (UWB) accesspoint 110 e.

The multi-radio device 102 may be enabled to generate and/or receiveradio-frequency (RF) signals in accordance with one or more RFtechnologies. The multi-radio device 102 may be enabled to perform, forexample, baseband signal processing in the processor 104. The processor104 may comprise suitable logic, circuitry and/or code that may beenabled to perform a variety of signal processing tasks and may includecontrolling of the radio transceivers 106 a through 106 c, for example.The memory 112 may comprise suitable logic, circuitry and/or code thatmay be enabled to store data and/or code that may be accessed by theprocessor 104 and/or the radio transceivers 106 a through 106 c (1-N).The radio transceiver 106 a may comprise suitable logic, circuitryand/or code that may be enabled to generate RF signals and intermediatefrequency (IF) signals from baseband signals, which may be communicatedfrom the processor 104, in accordance with a radio frequency technologyand/or standard. In addition, the radio transceiver 106 a may comprisesuitable logic, circuitry and/or code that may be enabled to receive RFsignals via one or more antennas, for example, antennas 108 a and 108 b,and convert the RF signals to baseband signals. The generated basebandsignals may be desirably formatted for further processing in theprocessor 104, for example.

The radio transceivers 106 b through 106 c (2-N) may be substantiallysimilar to radio transceiver 106 a but may operate in accordance withdifferent radio technologies. The radio transceivers 106 a through 106 c(1-N) may, for example, generate and/or receive signals in accordancewith cellular radio standards (UMTS, GSM, EDGE, HSDPA, EV-DO, CDMA 2000and others), broadband standards (for example WiMAX IEEE 802.16, WiBro),and short-range communication standards (WLAN IEEE 802.11, UWB, ZigBeeand others). In some instances, the radio transceivers 106 a though 106c may be enabled to conform with multiple radio frequency technologies,for example when a radio transceiver may be a software-defined radioplatform. The plurality of antennas communicatively coupled to themulti-radio device 102, for example antennas 108 a and 108 b, may becommunicatively coupled to one or more radio transceivers 106 a through106 c. Each radio transceiver may be communicatively coupled to at leastone antenna, and some antennas may be shared between a plurality of theradio transceivers 106 a, . . . , 106 c. Each of the radio transceiver106 a through 106 c may receive and/or transmit RF signals in accordancewith an RF technology to/from another device, for example, a cellularbasestation 110 a, a WiMAX basestation 110 b, a Bluetooth headphone 110c, a WLAN access point 110 d, and/or a UWB access point 110e. Inaccordance with various embodiments of the invention, the components ofthe multi-radio device 102 may be implemented in a single chip, or withmultiple chips and associated circuitry.

In many instances, downconverted baseband signals from the radiotransceivers 106 a through 106 c may initially be unsynchronized but mayneed to be synchronized and/or identified. In accordance with variousembodiments of the invention, synchronization may be achieved bycorrelating a received signal with a local signal, for example asynchronization signal.

FIG. 2 is a block diagram of an efficient full resolution correlator, inaccordance with an embodiment of the invention. Referring to FIG. 2,there is shown a plurality of delay blocks, of which delay blocks 202,204, 206, 216, 202 a, 204 a, 206 a, 202 b, 204 b, and 206 b may beillustrated. There are also shown adders 208, 208 a, 208 b and 212, andmultipliers 210, 210 a and 210 b. There is also shown input samplesx[n], delayed input samples x[n−(L−1)], x[n−(2L−1)] and x[n−(NL−1)],complex conjugate reference samples a*[0],a*[N−2] and a*[N−1], and acorrelation output signal r[n]. The symbol .* may denote the complexconjugate operation.

The delay blocks 202, 204, 206, 216, 202 a, 204 a, 206 a, 202 b, 204 b,and 206 b may be substantially similar. The delay block 202, forexample, may comprise suitable logic, circuitry and/or code that may beenabled to delay an input sample by one clock period. The adders 208,208 a, 208 b and 212 may be substantially similar and may be able togenerate an output signal that may be proportional to the sum of theinput signals. The multipliers 210, 210 a and 210 b may be substantiallysimilar and may comprise suitable logic, circuitry and/or code that maybe enabled to generate an output signal that may be proportional to theproduct of the input signals.

In many communication systems, timing synchronization may be important.For example, synchronization may be required between the received signaland a local signal at a receiver, for example a synchronization signal.In some instances, such systems may employ dedicated synchronizationsequences for timing synchronization. In order for synchronization to beachieved, received input samples, for example input samples x[n], may bematched to a synchronization sequence, for example s[n], by means of amatched filter and/or a correlator, for example. At time instances wherea correlation process may produce peaks in magnitude, the presence ofthe synchronization sequence may occur at the sampling instant in timewhere the matched filter (correlator) output magnitude may peak. Thereceived input samples x[n] and the synchronization sequence s[n] maycomprise a plurality of data symbols that may be over-sampled togenerate sequences of NL samples. For example, the input signal maycomprise N data symbols that may be oversampled by a factor L togenerate NL samples.

In some instances, more accurate localization in time may be achieved byperforming matched filtering (correlation) at a high over-sampling rateof the received signal. However, this may lead to undesirablecomputational complexity, as the matched filtering may have to beperformed over NL multiplications, which may be complex. This may resultin costly hardware, and the hardware cost may be growing, for example,exponentially with the over-sampling factor L. In the case of complexsequences, each of the complex multipliers may generate, for example,four multiplications and two additions.

The hardware cost may be reduced by down-sampling the received signal bya factor L, and matched filtering may be performed on N samples. Thismay, however, reduce the timing accuracy that may be achieved. In someinstances where high timing accuracy may be required, for example betterthan within 1-in-N samples, 1-in-NL accuracy may be achieved if thematched filtering may be performed at the sampling rate. In accordancewith various embodiments of the invention, the same 1-in-NL accuracy maybe achieved with a reduced number of multipliers, as described below.

To reduce the number of multipliers that may be required to perform thecorrelation operation, while retaining timing accuracy, the number ofsamples to represent the synchronization sequence s[n] may be reducedfrom NL samples by creating a reference sample sequence a[k] that maycomprise, for example, N coefficients. In accordance with variousembodiments of the invention, the new synchronization sequencecomprising the reference sample a[k] may be generated by the followingrelationship:

$\begin{matrix}{{a\lbrack k\rbrack} = {\sum\limits_{l = {kL}}^{{{({k + 1})}L} - 1}{s\lbrack l\rbrack}}} & (1)\end{matrix}$

where L may be the over-sampling factor, l ε {0, . . . , NL−1} and k ε{0, . . . , N−1}. Hence, the reference samples a[k] may be generatedfrom the original synchronization sequence s[n]. Similarly, the receivedinput samples x[n] may be reduced by a factor L, from NL samples to Nsamples by the following relationship:

$\begin{matrix}{{{y_{N - k}\lbrack n\rbrack} = {\sum\limits_{l = {n - {{({k - 1})}L}}}^{n - {({{kL} - 1})}}{x\lbrack l\rbrack}}};{k \leq N}} & (2)\end{matrix}$

where each y_(m)[n] may be generated as the sum of L samples from x[n],where l=0, . . . , NL. The generation of the samples y_(m)[n] may beachieved as illustrated in FIG. 2, for example. The adder 208, forexample, may generate y_(N−1)[n], and similarly the adders 208 a and 208b may generate y_(N−2)[n] and y₀[n].

The correlation output r[n] between the reference sample sequence a[k]and the generated sample sequence y_(m)[n] may be achieved by thefollowing relationship:

$\begin{matrix}{{{r\left( {l,n} \right)} = {\sum\limits_{m = {- \infty}}^{\infty}{a*\lbrack m\rbrack {y_{m - l}\lbrack n\rbrack}}}}{{r\lbrack n\rbrack} = {{r\left( {0,n} \right)} = {\sum\limits_{m = 0}^{N}{a*\lbrack m\rbrack {y_{m}\lbrack n\rbrack}}}}}} & (3)\end{matrix}$

where r(l,n) may denote a correlation coefficient at a shift l and atsample n. In accordance with various embodiments of the invention, theabove correlation may be performed at the over-sampling rate determinedby n, that is, at the same rate of the over-sampled signal x[n]. Becausethe generated sequences a[k] and y_(m)[n] may comprise N samples insteadof NL samples of the original sequences s[n] and x[n], there may be Ltimes fewer multiplications performed for the correlation given inequation (3), compared to correlating s[n] and x[n] directly. Asillustrated in FIG. 2, N multipliers, of which multipliers 210, 210 a,and 210 b may be illustrated. However, because the generated samplesequence y_(m)[n] may be updated at the over-sampling rate (as newsamples x[n] may enter the correlator), and the correlation coefficientr[n] may be generated at the over-sampling rate also, the correlationaccuracy may be similar to correlation with NL samples.

FIG. 3 is a flow chart illustrating an exemplary correlation process inaccordance with an embodiment of the invention. After initializing thealgorithm in step 302, reference samples a[k] may be generated fromsynchronization sequence s[n] in step 304. In step 306, the generatedsequence y_(k)[m] may be generated from the input samples x[n], asdescribed above for FIG. 2. In step 308, the reference samples a[k] maybe correlated with the generated sequence y_(k)[m] according to equation(3) shown above.

In accordance with an embodiment of the invention, a method and systemfor efficient full resolution correlation may comprise correlating afirst signal, for example y_(k)[n], with a second signal, for examplea*[k], at a rate corresponding to a first discrete signal, for examplex[n], wherein each sample of the first signal may be generated bysumming a plurality of consecutive samples from the first discretesignal and the second signal may be generated by summing the pluralityof consecutive samples from a second discrete signal, as described forFIG. 2. The correlating may be performed by a matched filter and/or acorrelator, as described for FIG. 2 and FIG. 3. The first signal, forexample y_(k)[n], comprising N samples may be generated by summing Lconsecutive samples for each of the N samples from the first discretesignal comprising N*L samples, for example x[n]. The second signalcomprising N samples, for example a*[k], may be generated by summing Lconsecutive samples for each of the N samples from the second discretesignal comprising N*L samples, as described for FIG. 2. The first signaly_(k)[n] and the second signal a*[k] may be correlated by multiplyingthe N samples of the first signal with the N samples of the secondsignal in N multipliers and summing a plurality of outputs of themultipliers, as illustrated in FIG. 2. A maximum of the correlating maybe determined to achieve synchronization between the first discretesignal and the second discrete signal.

Another embodiment of the invention may provide a machine-readablestorage, having stored thereon, a computer program having at least onecode section executable by a machine, thereby causing the machine toperform the steps as described herein for efficient full resolutioncorrelation.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputer system, or in a distributed fashion where different elementsare spread across several interconnected computer systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the computersystem such that it carries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A method for processing signals, the method comprising: correlating afirst signal with a second signal at a rate corresponding to a firstdiscrete signal, wherein each sample of said first signal is generatedby summing a plurality of consecutive samples from said first discretesignal, and wherein said second signal is generated by summing saidplurality of consecutive samples from a second discrete signal.
 2. Themethod according to claim 1, wherein said correlating is performed by amatched filter.
 3. The method according to claim 1, wherein saidcorrelating is performed by a correlator.
 4. The method according toclaim 1, comprising generating said first signal comprising N samples bysumming L consecutive samples for each of said N samples from said firstdiscrete signal comprising N*L samples.
 5. The method according to claim4, comprising generating said second signal comprising N samples bysumming L consecutive samples for each of said N samples from saidsecond discrete signal comprising N*L samples.
 6. The method accordingto claim 5, comprising correlating said first signal and said secondsignal by multiplying said N samples of said first signal with said Nsamples of said second signal in N multipliers and summing a pluralityof outputs of said multipliers.
 7. The method according to claim 1,comprising determining a maximum of said correlating to achieve asynchronization between said first discrete signal and said seconddiscrete signal.
 8. A system for processing signals, the systemcomprising: one or more circuits that enable correlation of a firstsignal with a second signal at a rate corresponding to a first discretesignal, wherein each sample of said first signal is generated by summinga plurality of consecutive samples from said first discrete signal, andwherein said second signal is generated by summing said plurality ofconsecutive samples from a second discrete signal.
 9. The systemaccording to claim 8, wherein said one or more circuits comprise amatched filter that enables said correlation.
 10. The system accordingto claim 8, wherein said one or more circuits comprise a correlator thatenables said correlation..
 11. The system according to claim 1, whereinsaid one or more circuits enables generation of said first signalcomprising N samples by summing L consecutive samples for each of said Nsamples from said first discrete signal comprising N*L samples.
 12. Thesystem according to claim 11, wherein said one or more circuits enablesgeneration of said second signal comprising N samples by summing Lconsecutive samples for each of said N samples from said second discretesignal comprising N*L samples.
 13. The system according to claim 12,wherein said one or more circuits comprises N multipliers, and said onemore circuits enables said correlation of said first signal and saidsecond signal by multiplying said N samples of said first signal withsaid N samples of said second signal in said N multipliers and summing aplurality of outputs of said N multipliers.
 14. The system according toclaim 8, comprising determining a maximum of said correlating to achievea synchronization between said first discrete signal and said seconddiscrete signal.
 15. A machine-readable storage having stored thereon, acomputer program having at least one code section executable by amachine, said at least one code section enabling: correlating a firstsignal with a second signal at a rate corresponding to a first discretesignal, wherein each sample of said first signal is generated by summinga plurality of consecutive samples from said first discrete signal, andwherein said second signal is generated by summing said plurality ofconsecutive samples from a second discrete signal.
 16. Themachine-readable storage according to claim 15, wherein said correlatingis performed by a matched filter.
 17. The machine-readable storageaccording to claim 15, wherein said correlating is performed by acorrelator.
 18. The machine-readable storage according to claim 15,comprising generating said first signal comprising N samples by summingL consecutive samples for each of said N samples from said firstdiscrete signal comprising N*L samples.
 19. The machine-readable storageaccording to claim 18, comprising generating said second signalcomprising N samples by summing L consecutive samples for each of said Nsamples from said second discrete signal comprising N*L samples.
 20. Themachine-readable storage according to claim 19, comprising correlatingsaid first signal and said second signal by multiplying said N samplesof said first signal with said N samples of said second signal in Nmultipliers and summing a plurality of outputs of said multipliers. 21.The machine-readable storage according to claim 15, comprisingdetermining a maximum of said correlating to achieve a synchronizationbetween said first discrete signal and said second discrete signal.